The present invention relates to an improved fiber glass composition. More particularly the invention is directed to a fiber glass composition including an improved resin binder having an enhanced cure rate. The improved binder also enables manufacture of a fiber glass composition exhibiting enhanced uncured storage properties, increased thermal stability, and reduced corrosiveness to metals.
Fiber glass compositions find significant use as acoustical or thermal insulation in a wide variety of commercial applications. Generally fiber glass compositions are prepared by applying a resin binder composition including a resole (phenol-formaldehyde) resin and a catalyst to hot glass fibers; the binder-coated glass fibers are collected in the form of a non-woven fiber glass blanket. The fiber glass blanket is thereafter compressed and heated to cure the binder composition either in an oven (xe2x80x9cline curexe2x80x9d) to form batts or boards or in a mold to form shaped fiber glass articles. During the heating step, the resin binder composition dispersed on the glass fibers polymerizes to form an infusible, cured resin solid that binds the glass fibers where they overlap to impart strength and resiliency to the fiber glass product. Molded fiber glass articles thus retain their molded, compressed shape after they are removed from the mold.
Fiber glass blankets, sometimes referred to as xe2x80x9cmolding stock,xe2x80x9d are often manufactured, stored in an uncured state as a compact roll and subsequently sold to off-site fiber glass manufacturing operations where they are used to manufacture molded fiber glass articles. When the rolled fiber glass blankets are unrolled after a period of storage, they often do not lie flat, and their surface exhibits a frayed or napped appearance. That condition is usually attributed to premature curing of the raw resin binder during blanket storage. Fiber glass blankets exhibiting such characteristics typically do not provide molded fiber glass articles having the physical properties, i.e., the flexural, tensile and compressive strengths exhibited by molded fiber glass articles prepared from fiber glass blankets immediately after their manufacture.
There has been significant research and development efforts directed to improving resin binder compositions useful in the manufacture of fiber glass articles. The present invention is based on the development and use of novel catalyzed resin binder compositions that not only enable enhanced storage life for uncured fiber glass blankets, but also exhibit longer xe2x80x9cpot lifexe2x80x9d in the fiber glass blanket production line. Yet, surprisingly, the uncured catalyzed resin binder compositions of this invention also exhibit a demonstrably faster rate of heat-induced cure, and the cured binder compositions exhibit advantageous chemical/mechanical properties. Fiber glass products formed using such binders exhibit reduced corrosivity in standardized tests. Further, in preferred embodiments, the present binder compositions can be used in significantly reduced amounts (relative to the usage levels of state-of-the-art resin binders) in fiber glass blanket manufacture without substantial compromise of physical strength characteristics. Lower resin binder usage levels enables production of fiber glass articles with improved thermal stability.
The novel catalyzed resin binder composition in accordance with this invention is an aqueous solution of a resole (phenol-formaldehyde) resin and about 2 to about 10 parts per weight on a solids basis of a catalyst consisting essentially of a salt formed from ammonia and an aryl sulfonic acid. The binder optionally, but preferably, includes as well a compound selected from the group consisting of urea, melamine and dicyandiamide or combinations thereof. The resin binder composition is characterized by a cure rate which is about 10 to about 50% faster than a binder of identical resin composition, but with an equivalent amount of ammonium sulfate as an acid catalyst. The chemical/mechanical properties of the improved resin binder composition allow preparation of fiber glass compositions exhibiting advantage in many applications.
In one embodiment of the present invention, there is provided a process of preparing fiber glass blankets characterized by their improved storage stability as evidenced by the flexural, tensile and compressive strengths of molded fiber glass compositions formed by heating and compressing the blanket after a predetermined storage period. The storage stable fiber glass blanket is prepared using the improved aqueous resin binder composition comprising a resole resin and about 2 to about 10 parts per weight on a solids basis of a catalyst consisting essentially of a salt formed from ammonia and an aryl sulfonic acid. The glass fibers are coated with the resin binder composition, and the binder-coated glass fibers are collected in the form of a non-woven blanket including an effective amount (generally up to about 25% by weight) on a solids basis of the resin binder.
In high temperature applications, for example, pipe insulation for high temperature steam pipes, the cured resin binder composition in the fiber glass insulation can decompose exothermally resulting in high localized temperatures that can soften and/or melt the glass fibers and form voids in the insulating composition. The result is loss of insulating capacity. There is also provided in accordance with the present invention a fiber glass composition having enhanced thermal stability and a method of preparation thereof. Typically molded fiber glass articles are manufactured using a predetermined amount of a resole resin binder composition relative to the weight of fiber glass. In one embodiment of this invention, fiber glass compositions are formed using less than the predetermined amount of the improved binder composition. The resulting fiber glass compositions having reduced binder content are compressed and heated to form fiber glass articles having enhanced thermal stability and without significant loss of structural strength.
Many fiber glass compositions are used as acoustical or thermal insulation in direct contact with steel or other metal surfaces. Components of the cured resin binder composition may leach out of the fiber glass insulation and promote corrosion of adjacent metal surfaces. Thus, in another related embodiment of the present invention there is provided a fiber glass composition characterized by low corrosiveness as assessed by either ASTM C665.98 xc2xa7 13.8 or ASTM C795-92 and a process for preparing such non-corrosive fiber glass compositions.